The present invention refers to a window regulator for motor vehicles.
Window regulators in which raising and lowering movements of the window are obtained by a threaded shaft and nut screw transmission, are known from the outset of the automotive industry.
When the motor vehicles were equipped by sliding flat windows, the transmissions were easy to made since the threaded shaft and the window were parallel to each other and it was enough to interconnect them by a rigid driving member. One example, between the many, is given in U.S. Pat. No. 1,627,331, published in 1927.
With the coming of bent windows many manufacturers tried to maintain the threaded shaft and nut screw transmissions by striving to make window regulators equipped by interconnection means between the nut screw and the driving member, which were able to ensure the interconnection of the driving member and the nut screw independently of the variable distance between them.
Examples of these interconnection means are given in prior documents FR-A-1 294 605 and FR-A-2 431 594 (and corresponding GB-A-2 026 597).
According to FR-A-1 294 605, the interconnection means comprise a resilient blade constituting a leaf spring the middle portion of which is fixed to the nut screw and the ends of which are provided with small rollers sliding in corresponding horizontal slits of a support and driving bracket of the window.
According to FR-A-2 431 594, the interconnection means comprise two box shaped bodies, one of which, the outer one, is fastened to the nut screw and the other of which, the inner one, is connected to a support and driving bracket of the window and is slidable telescopically in the inner body according to a direction perpendicular to the axis of the threaded shaft. An intermediate bracket provided with small rollers having a cuntersunk groove, in which a rail is engaged which form part of the support and driving bracket of the window, is fastened to the inner box shaped body. The cuntersunk shape of the groove of the small rollers allows a reciprocal oscillation of the two brackets to take place, in order to fit the bending of the window.
The modern trend of the automotive industry is to adopt more and more bent windows, so that the solutions proposed in the two prior documents FR-A-1 294 605 and FR-A-2 431 594, besides being relatively complex, badly lend to be fitted to very bent windows: in the first case, the resilient blade can assume with difficultly a maximum camber corresponding to the zone in which its connection point to the window is more far away from the threaded shaft; in the second case, the telescopic sliding travel of the body fastened to the window and the oscillation amplitude allowed by the small grooved rollers cannot exceed a preset limit.
From EP-A-0 384 685 and corresponding U.S. Pat. No. 5,012,613 a threaded shaft and nut screw window regulator for strongly bent windows is known, in which the threaded shaft is bent and is fixed. A nut screw is contained in a gearcase which is fastened to a support and driving bracket of the window and which is raised and lowered together with the bracket, according to the bent path of the window. The nut screw has the shape of a gearwheel having a helical peripheral toothing which meshes with a worm screw contained in the gearcase. The nut screw is connected to a fixed electric motor through a flexible driving shaft, the axis of which can be deformed in order to fit the variable distance between the motor and the gearcase.
The solution of EP-A-0 384 685 and U.S. Pat. No. 5,012,613 has the drawback to require a bent, relatively expensive, threaded shaft, and the use of a flexible driving shaft with a deformable axis enduring cyclical deformations in operation, which may cause its breaking. Moreover, the weight of its reduction box, which is raised and lowered together with the window, undesirably increases the weight of the movable unit of the window.